Preparing for the unexpected?

Unravelling complex changes in marine ecosystems due to increasing human influence is the focus of the latest themed set of papers in ICES Journal of Marine Science.
Published: 22 July 2020

​One of the most important challenges facing ecosystem management today is the development of effective management strategies to cope with the increasing potential for complex and unexpected changes and still be able to preserve critical marine ecosystem services.​

​​Increasing amounts of observational data and powerful new mathematical approaches promise to substantially advance the development of strategies able to support sustainable management of marine ecosystems.

The challenge of how to move towards applied management strategies that include the possibility of unexpected changes, evolution, and adaptation provides the focus point for the latest ICES Journal of Marine Science themed set, “Science in a nonlinear, nonequilibrium world". Spearheaded by Gary Griffith, the Norwegian Polar Institute,  a compilation of nine peer-reviewed paper are presented on thoughts, new methods, and applied research.

This new research will support ongoing discussions to inform marine management and policy on the need for a paradigm shift in management practices to include the “nonlinear nonequilibrium" perspective. Dispelling the mystery of nonlinear dynamics, nonlinearity in stock recruitment, ecological indicators to detect sudden changes and participatory management frameworks to consider nonlinearity and uncertainty are a few of the research topics covered. Griffith introduces the themed set​, where he focuses on, "on three important areas—causality, prediction, and emergence—where a “non-linear” perspective can advance our understanding and better support sustainable management of ecosystems". A comprehensive overview, this is a good starting point for the reader​. 

Chaos theory to reconcile scientists and non-scientists​

Over the last 30 years, the concepts of non-linearity and deterministic chaos have transformed ecological modelling. What has been achieved, in particular under the name of empirical dynamical modelling (EDM), responds to some of the issues that were originally highlighted, but not to all of them.

"Thirty years ago, it was hoped that non-linear thinking could help bring fishing professionals and scientists together​ around the concept of indeterminism" says Christian Mullon (MARBEC) who has co-authored, Modelling chance and necessity in natural systems, with Benjamin Planque (Institute of Marine Research​​). "While it is usual for fishers to expect some level of unpredictability in the resource, nonlinear approaches and deterministic chaos provide a way for fisheries scientists to represent such indeterminacy.​​"

Mullon notes that nonlinear models are still rarely operational in fisheries today. "The model we are proposing is a step aside. Its main aim is to promote an open dialogue between fishers and scientists through the simple ideas of chance and necessity, that are familiar to all the actors (although they may have different views one these issues). The modelling approach can be used to reconstruct the possible dynamics of an ecological system taking explicitly into account available observations, their uncertainties and the assumptions that have been made. Ultimately, the resulting model is not a tool provided by scientists to fishers but rather a tool that is jointly elaborated by both parties. We observe together, and we learn together." ​

Non-linearity in stock–recruitment relationships

Camilla Sguotti (University of Hamburg) welcomed the opportunity to contribute to this themed set with Non-linearity in stock–recruitment relationships of Atlantic cod: insights from a multi-model approach, which she views shedding light on the presence of non-linear dynamics in marine systems and offering a set of methods to model and understand them. “We have witnessed major changes in ecosystems worldwide and major irreversible reorganizations of marine ecosystems with consequent socio-economic changes - this shows that we live in a non-equilibrium/non-linear world that we need to be able to understand and model in order to face the challenges of climate change while being able to sustainably exploit our marine resources. Even though it is now well-established that the natural world is mainly dominated by non-linear and chaotic processes, the inclusion of these types of dynamics into management is still difficult and seldom done. To avoid management failure and both ecological and socio-economic surprises, we need to develop/apply new methods which can take these type of dynamics into account."​

Sguotti’s paper looks at a multi-model approach applied to the “typical” fishery problem of the stock-recruitment relationship. “The stock-recruitment relationship is the basis of every stock assessment and therefore management approach, but it is still difficult to model as it is not clear what form this relationship has.  Our paper compares three very different approaches to model and predict the SR relationship of 20 stocks of Atlantic cod: the standard Ricker model, stochastic cusp models which originate from catastrophe theory, and a data driven approach from the Empirical Dynamic Modelling framework, called Simplex Projection. We have also integrated environmental drivers, which are known to affect recruitment and productivity but are seldom included in stock assessment. Our results show that different models need to be applied to different dynamics if we want to have more powerful analyses and more trustable predictions, important elements for a successful management.” 

The latest issue of ICES Journal of Marine Science features two themed sets, Science in support of a nonlinear non-equilibrium world andApplications of machine learning and artificial intelligence in marine scienceBoth themed sets are free to access for all readers.

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Preparing for the unexpected?

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